Put out feeler to your partner

 How to make sure that your partner are willing to have a three way? Create some illusions, such as there is a third person joining your sexual process. Let your partner blindfold when making love and tie him/her to the bed to make sure they are unable to break free. Pretend to open the door and talk to others. In fact, you are the only one at there, then don't talk and walk into the room. Try to touch her/he in a different way and kiss her/him gently. In this way he/she will experience a special threesome sex, just like making love with a stranger.